Repulsion type circuit breaker control device

ABSTRACT

A repulsion type circuit breaker movable contact device comprising a first movable contact, an opening/closing mechanism which drives the first movable contact for opening and closing, a second movable contact for contacting the first movable contact, the second movable contact being freely pivotable and adapted to receive an electromagnetic repulsion force from said first movable contact, and a contact spring comprising a twisted coil spring disposed with its twisting fulcrum displaced from the rotational pivot of the second movable contact, the contact spring urging the second movable contact into contact with the first movable contact, whereby upon flow of a predetermined mount of electric current through the first and second movable contacts, the electromagnetic repulsion force moves the second movable contact apart from the first movable contact.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a repulsion type circuit breakerprovided with a first movable contact which is opened and closed by anopening/closing mechanism and a second movable contact which isdisconnected from the first movable contact by an electromagneticrepulsion force, specifically a contact device which is adapted so thatupon extreme current flow disconnection of the second movable contactmay not be obstructed by the contact spring which urges the first andsecond movable contacts together.

2. Discussion of the Related Art

FIGS. 4 and 5 both show the side view of the conventional contact devicein a closed condition. In FIG. 4, the first movable contact 1 ispivotably secured to the main casing 2 by the holder (not shown) anddriven for opening and closing by the opening/closing mechanism (notshown). The second movable contact 3 which comes in contact with thefirst movable contact 1 is V-shaped as viewed from the side and ispivotably secured at its comer to the second movable contact support 5by the pivotal pin 4. The second movable contact support 5 is fixed tothe main casing 2 with a screw 6. The second movable contact 3 iselectrically connected to a terminal plate 8 at the power supply sidewith a lead wire 7, and the terminal plate 8 is fixed to the main casing2 with a screw 9. The contact spring 10 comprises a double tortionaltwisted coil spring with two arms 10a fixed to the second movablecontact support 5, a U-bent pan 10b engaged with the second movablecontact 3, and a coil 10c between each arm 10a and the U-bent part 10b.The contact spring 10 is mounted about the pivotal pin 4. Thus, thecontact spring 10 urges the second movable contact 3 in the clockwisedirection toward the first movable contact 1 to maintain a requiredcontact pressure. Contact edges 1a and 3a are provided respectively onthe first movable contact 1 and the second movable contact 3.

FIG. 5 shows another example of the conventional contact device in whicha compression coil spring used as the contact spring 10 is insertedbetween the bar type second movable contact 3 and the terminal plate 8.The second movable contact 3 is pivotably secured at its end to thesecond movable contact support 5 by the pivotal pin 4. Electricalconnection between the second movable contact 3 and the second movablecontact support 5 is maintained by sliding contact, and between theterminal plate 8 and the second movable contact support 5 by directconnection.

In the configurations shown in FIGS. 4 and 5, the current flows inopposite directions, as shown with arrowheads, in mutually parallelconductive parts of first movable contact 1 and second movable contact3. An electromagnetic force is created by these currents causing firstmovable contact 1 and second movable contact 3 to repel each other. Therepulsion type circuit breaker uses this electromagnetic repulsion forceto turn second movable contact 3 in the counterclockwise directionagainst contact spring 10 to quickly disengage contact edges 1a and 3awhen current flow reaches a predetermined mount. The circuit formedbetween contact edges 1a and 3a is thereby broken interrupting any largecurrent flow such as a shorting current.

In such a repulsion type circuit breaker, when second movable contact 3is disconnected by the electromagnetic repulsion force, contact spring10 still urges the second movable contact 3 in opposition to theelectromagnetic repulsion force used to open the circuit. In the case ofthe conventional circuit breaker, the amount of electromagneticrepulsion force required to overcome, the reactive force of contactspring 10 increases as the spring is compressed. The increasing forcerequired to bend the spring has been a substantial obstacle in reducingthe disconnection time of the second movable contact.

SUMMARY OF THE INVENTION

The present invention has been made in view of the above circumstancesand has an object to provide a contact device of a repulsion typecircuit breaker for which the reactive force of the contact spring isnot substantially increased when the second movable contact isdisconnected thereby quickening disconnection by electromagneticrepulsion force and thus improving current interruption performance.

Additional objects and advantages of the invention will be set forth inpart in the description which follows and in part will be obvious fromthe description, or may be learned by practice of the invention. Theobjects and advantages of the invention may be realized and attained bymeans of the instrumentalities and combinations particularly pointed outin the appended claims.

To achieve the objects and in accordance with the purpose of theinvention, as embodied and broadly described herein, the repulsion typemovable contact device of this invention comprises a first movablecontact, an opening/closing mechanism which drives the first movablecontact for opening and closing, a second movable contact for contactingthe first movable contact, the second movable contact being freelypivotable and adapted to receive an electromagnetic repulsion force fromsaid first movable contact, and a contact spring comprising a twistedcoil spring disposed with its .[.twisting fulcrum.]. .Iadd.point ofapplication for twisting .Iaddend.displaced from the rotational pivot ofthe second movable contact, the contact spring urging the second movablecontact into contact with the first movable contact, whereby upon flowof a predetermined mount of electric current through the first andsecond movable contacts, the electromagnetic repulsion force moves thesecond movable contact apart from the first movable contact.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated into and constitute apart of this specification illustrate embodiments of the invention and,together with the description, serve to explain the objects, advantagesand principles of the invention. In the drawings,

FIG. 1 is a cross-sectional view of an embodiment of the presentinvention showing the principal part of the repulsion type circuitbreaker;

FIG. 2(A) is a side view of an embodiment of the present inventionshowing the contact device of the circuit breaker in a closed condition;

FIG. 2(B) is a side view of an embodiment of the present inventionshowing the contact device of the circuit breaker in an openedcondition;

FIG. 3 is a side view of another embodiment of the of present invention;

FIG. 4 is a side view of an example of the conventional contact device;and

FIG. 5 is a side view of another example of the conventional contactdevice.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the conventional construction, the length of the arm from the pivotalpoint of the second movable contact to the acting point of the resilientforce of the contact spring is fixed and any increase of resilient forceof the contact spring directly results in an increase of the reactiveforce against disconnection. In the present invention, the contactspring is formed with a twisted coil spring, and the .[.twistingfulcrum.]. .Iadd.point of application twisting .Iaddend.is displacedfrom the pivotal point of the second movable contact to reduce thereactive force on the contact spring as the second movable contact isdisconnected from the first movable contact.

To cause the resilient force of the contact spring to act on the secondmovable contact, the device can be constructed so that a pin is plantedin the second movable contact and engaged with the arm of the contactspring.

In the conventional construction, the contact spring which comprises atwisted coil spring is mounted on the pivotal pin of the second movablecontact. Therefore, the length of the arm of the spring from the pivotalpin to the acting point of the resilient force of the contact spring issubstantially fixed. When the contact spring is twisted due todisconnection of the second movable contact from the first movablecontact and the resilient force of the spring increases, such increasedirectly results in an increase of reactive force against disconnectionof the second movable contact. In addition, the turning angle of thesecond movable contact and the deforming angle due to twisting of thecontact spring along with disconnection coincide with each other andtherefore the reactive force increases in approximate proportion to theopening distance of the second movable contact.

On the other hand, the configuration in accordance with the presentinvention allows the length of the arm from the pivotal point of thesecond movable contact to the acting point of the resilient force of thecontact spring to be reduced when the second movable contact turns. Thisreduction is accomplished by displacing the turning fulcrum of thecontact spring from the pivotal point of the second movable contact.Thus, the reactive force exerted by the contact spring is reduced ascompared to that of the conventional device during rotation of thesecond movable contact. Furthermore, the twisting deformation angle ofthe contact spring can be controlled to be smaller than the turningangle of the second movable contact, thereby further reducing thereactive force required to disengage the second movable contact.

If the contact device is constructed so that the pin planted in thesecond movable contact engages with the arm of the contact spring inorder to make the resilient force of the contact spring act on thesecond movable contact, the portion of the ann between the contactspring turning fulcrum and the pin is reduced during rotationaldisconnection of the second movable contact.

The present invention provides a circuit breaker with a high currentbreaking capacity which can use the electromagnetic repulsion force tothe maximum extent since the reactive force of the contact springagainst the electromagnetic repulsion force is reduced compared toconventional device during disconnection of the second movable contact.

The following describes the preferred embodiments of the presentinvention shown in FIGS. 1 through 3. The reference numerals are used torepresent parts corresponding to the examples of the conventional deviceshown in FIGS. 4 and 5.

FIG. 1 is a cross-sectional view of the principal partof the repulsiontype circuit breaker provided with the contact device in accordance withthe present invention in a closed position. A first movable contact 1 ispivotably secured by a holder 11 to a main casing 2 which is made ofmolded resin. The opening/closing mechanism 12 drives the first movablecontact 1 around holder 11. Holder 11 thus acts as a fulcrum for thefirst movable contact 1. A second movable contact 3 which comes incontact with first movable contact 1 via contact edges 1a and 3a ispivotably secured to a pair of right and left second movable contactsupports 5 by a pivotal pin 4. Second movable contact supports 5, whichslidingly contact second movable contact 3 from right and left sides,are coupled by brazing to both sides of a terminal plate 8 at the powersupply side. Terminal plate 8 is fixed to main using 2 with screws 6 and9.

A contact spring 10, which energizes the second movable contact 3 in theclockwise direction to provide contact pressure between first movablecontact 1 and second movable contact 3, may comprise a double torsionaltwisted coil spring. Contact spring 10 is U-shaped with two arms 10a, aU-shaped portion 10b, and a coil 10c between the U-shaped portion 10band each arm 10a. A support pin 13 which secures contact spring 10 to aspring block 14 at coil 10c is displaced from pivotal pin 4. A springblock 14 is fixed to main casing 2 with a screw 15. U-shaped portion 10bof contact spring 10 is fixed to spring block 14, and arms 10a areengaged with the right and left protruding ends of pin 16 which isplanted in second movable contact 3. An arc suppressing chamber 17 isarranged to surround the first and second movable contacts 1 and 3, anda molded resin cover 18 is fitted to main casing 2.

When a large current such as a shorting current flows through a circuitbreaker as described above, a large electromagnetic repulsion force(shown with large unshaded arrowheads) acts between the currents flowingin opposite directions in first movable contact 1 and second movablecontact 3 (shown with thin arrowheads). Before first movable contact 1is driven by opening/closing mechanism 12, second movable contact 3 isdriven in the counterclockwise direction to be disconnected from firstmovable contact 1. In this case, pin 16 slides along the arms 10atowards coil 10c while contact spring 10 is slightly twisted anddeformed in the counterclockwise direction. The location of pin 16before and after rotation of second movable contact 3 is shown in FIGS.2(A) and 2(B), respectively.

FIG. 2 illustrates the function of this configuration in accordance withthe present invention. FIG. 2(A) shows the closed condition of theembodiment, and FIG. 2(B) shows the opened condition of the embodiment.In FIG. 2(A), since the coefficient of friction between pin 16 and arms10a of contact spring 10 is extremely small, the force exerted bycontact spring 10 acts at approximately right angles to pin 16. Assumingthat this force is F₁ and that the length of arms 10a from pivotal point4 to pin 16 which is the acting point of force F_(l) ₁, the .[.angularmovement in the clockwise direction.]. .Iadd.rotation movement forclockwise motion .Iaddend.which acts on second movable contact 3 underthe closed condition is F₁ ×l₁. In FIG. 2(B), similarly, assuming thatthe force exerted by contact spring 10 and that the length of the arm upto the point of action are F₂ and l₂, respectively, the .[.angularmovement in the clockwise direction.]. .Iadd.rotation moment forclockwise motion .Iaddend.which acts on the second movable contact 3upon disconnection is F₂ ×l₂.

When contact spring 10 is twisted and deformed in the counterclockwisedirection with support pin 13 acting as a .[.twisting fulcrum.]..Iadd.point of application for twisting..Iaddend., F₁ is smaller thanF₂. However, arms 10a of contact spring 10 are only positioned slightlyinside the movement arc C, of pin 16 and, therefore, the twistingdeformation angle of contact spring 10 around support pin 13 is smallerthan the turning angle of second movable contact 3. For this reason, F₂is not substantially greater than F₁, whereas the increase in force ismuch more in a conventional device since the coil of the spring ismounted on the rotational pin of the second movable contact thusrequiring more spring deformation.

Furthermore, the active length l₂ of arms 10a after disconnectionbecomes far smaller than l₁, as shown, since pin 16 moves along arms 10aof contact spring 10. Consequently, the magnitude of the .[.angular.]..Iadd.rotation .Iaddend.moments in FIGS. 2(A) and 2(B), respectively,appears as F₁×l₁ >F₂ ×l₂, and this reaction of contact spring 10 isreduced during disconnection and separation of second movable contact 3.

Referring to FIG. 3 showing another embodiment of the present invention,second movable contact 3 and terminal plate 8 are electrically connectedwith a lead wire 7 instead of a sliding contact between second movablecontact 3 and movable contact supports 5. The descriptions of otherconfigurations and functions are omitted since they are similar to thatshown in FIG. 1.

As described above, the configuration of FIGS. 1-3 provides quickerdisconnection of the second movable contact than conventional contactdevice since the reactive force from contact spring 10 is reduced as thesecond movable contact 3 is driven and disconnected by theelectromagetic repulsion force. In addition, the acting point of theresilient force of the contact spring 10 can be smoothly shifted duringdisconection by planting pin 16 in the second movable contact 3 andengaging it with arms 10a of contact spring 10.

The foregoing description of preferred embodiments of the invention hasbeen presented for purposes of illustration and description. It is notintended to be exhaustive or to limit the invention to the invention tothe precise form disclosed, and modifications and variations arepossible in light of the above teachings or may be acquired frompractice of the invention. The embodiments were chosen and described inorder to explain the principles of the invention and its practicalapplication to enable one skilled in the art to utilize the invention invarious embodiments and with various modifications as are suited to theparticular use contemplated. It is intended that the scope of theinvention be defined by the claims appended hereto, and theirequivalents.

What is claimed is:
 1. A repulsion type circuit breaker movable contactdevice comprising:a first movable contact; an opening/closing mechanismoperably attached to said first movable contact for driving said firstmovable contact between an open and a closed position; a second movablecontact for contacting said first movable contact when said firstmovable contact is in said closed position, said second movable contactbeing freely pivotable and adapted to receive an electromagneticrepulsion force from said first movable contact; and a twisted torsionalcoil contact spring disposed with its .[.twisting fulcrum.]. .Iadd.pointof application for twisting .Iaddend.displaced from the rotational pivotof said second movable contact, said contact spring urging said secondmovable contact into contact with said first movable contact, wherebyupon flow of a predetermined amount of electric current through saidfirst and second movable contacts, the electromagnetic repulsion forcemoves said second movable contact apart from said first movable contact.2. A repulsion type circuit breaker movable contact device as in claim1, wherein a pin is disposed in said second movable contact and an armof said contact spring is engaged with said pin.
 3. A repulsion typecircuit breaker movable contact device as in claim 1, wherein a pin isdisposed in said second movable contact and said contact spring includesa U-shaped portion, two arms and a coil disposed between said U-shapedportion and each of said arms, each of said arms engaged with said pin.4. A repulsion type circuit breaker movable contact device as in claim1, wherein said second movable contact is freely pivotable about arotation .[.peg.]. .Iadd.pin disposed at the rotational pivot and.Iaddend.secured by at least one movable contact support from which saidsecond movable contact receives electrical current through slidingcontact.
 5. A repulsion type circuit breaker movable contact device asin claim 2, wherein said second movable contact is freely pivotableabout a rotationn .[.peg.]. .Iadd.pin disposed at the rotational pivotand .Iaddend.secured by at least one movable contact support from whichsaid second movable contact receives electrical current through slidingcontact.
 6. A repulsion type circuit breaker movable contact device asin claim 3, wherein said second movable contact is freely pivotableabout a rotation .[.peg.]. .Iadd.pin disposed at the rotational pivotand .Iaddend.secured by at least one movable contact support from whichsaid second movable contact receives electrical current through slidingcontact.
 7. A repulsion type circuit breaker movable contact device asin claim 1, wherein a lead wire connected to said second movable contactprovides electrical current to said second movable contact.
 8. Arepulsion type circuit breaker movable contact device as in claim 2,wherein a lead wire connected to aid second movable contact provideselectrical current to aid second movable contact.
 9. A repulsion typecircuit breaker movable contact device as in claim 3, wherein a leadwire connected to said second movable contact provides electricalcurrent to said second movable contact.
 10. A repulsion type circuitbreaker movable contact device as in claim 2, wherein upon the movingapart of the first and second movable contacts, said pin slides alongsaid arm towards said contact spring .[.twisting fulcrum.]. .Iadd.pointof application for twisting.Iaddend..
 11. A replusion type circuitbreaker movable contact device as in claim 3, wherein upon the movingapart of the first and second movable contacts, said pin slides alongsaid arms towards said contact spring coil.
 12. A repulsion type circuitbreaker movable contact device as in claim 1, wherein said contactspring exerts a force and .[.an annular.]. .Iadd.a rotational.Iaddend.moment on said second movable contact, the .[.annular.]..Iadd.rotation .Iaddend.moment decreasing upon movement of contact, thesaid second movable contact by the electromagnetic repulsion force..Iadd.
 13. A repulsion type circuit breaker movable contact devicecomprising:an opening/closing mechanism operably attached to said firstmovable contact for driving said first movable contact between an openposition and a closed position; second movable contact for contactingsaid first movable contact when said first movable contact is in saidclosed position, said second movable contact being freely pivotable andadapted to receive an electromagnetic repulsion force from said firstmovable contact; and a contact pressure applying member for applying acontact force to urge said second movable contact into contact with saidfirst movable contact, wherein the flow of a predetermined amount ofelectric current through said first and second movable contacts producesthe electromagnetic repulsion force with sufficient magnitude to movesaid second movable contact apart from said first movable contact, andwherein said contact pressure applying member exerts an annular momenton said second movable contact, the annular moment decreasing uponmovement of said second movable contact by the electromagnetic repulsionforce. .Iaddend..Iadd.14. A repulsion type circuit breaker movablecontact device as in claim 13, further including a pin disposed in saidsecond movable contact and an arm provided on said contact pressureapplying member in engagement with said pin. .Iaddend..Iadd.15. Arepulsion type circuit breaker movable contact device as in claim 13,further including a pin disposed in said second movable contact, aU-shaped portion on said contact pressure applying member, two armsengaged with said pin, and a coil disposed between said U-shaped portionand each of said arms. .Iaddend..Iadd.16. A repulsion type circuitbreaker movable contact device as in claim 13, wherein said secondmovable contact is freely pivotable about a rotation pin disposed at therotational pivot of said second movable contact and secured by at leastone movable contact support, said second movable contact receivingelectrical current through sliding contact. .Iaddend..Iadd.17. Arepulsion type circuit breaker movable contact device as in claim 14,wherein said second movable contact is freely pivotable about a rotationpin disposed at the rotational pivot of said second movable contact andsecured by at least one movable contact support, said second movablecontact receiving electrical current through sliding contact..Iaddend..Iadd.18. A repulsion type circuit breaker movable contactdevice as in claim 15, wherein said second movable contact is freelypivotable about a rotation pin disposed at the rotational pivot of saidsecond movable contact and secured by at least one movable contactsupport, said second movable contact receiving electrical currentthrough sliding contact. .Iaddend..Iadd.19. A repulsion type circuitbreaker movable contact device as in claim 13, further including a leadwire connected to said second movable contact to provide electricalcurrent to said second movable contact. .Iaddend..Iadd.20. A repulsiontype circuit breaker movable contact device as in claim 14, furtherincluding a lead wire connected to said second movable contact toprovide electrical current to said second movable contact..Iaddend..Iadd.21. A repulsion type circuit breaker movable contactdevice as in claim 15, further including a lead wire connected to saidsecond movable contact to provide electrical current to said secondmovable contact. .Iaddend..Iadd.22. A repulsion type circuit breakermovable contact device as in claim 14, wherein said contact pressureapplying member has a point of application for twisting, and whereinupon the moving apart of the first and second movable contacts, said pinslides along said arm towards said point of application for twisting..Iaddend..Iadd.23. A repulsion type circuit breaker movable contactdevice as in claim 15, wherein said contact pressure applying memberincludes a coil, and wherein upon the moving apart of the first andsecond movable contacts, said pin slides along said arms towards saidcoil. .Iaddend..Iadd.24. A repulsion type circuit breaker movablecontact device comprising:a first movable contact; an opening/closingmechanism operably attached to said first movable contact for drivingsaid first movable contact between an open and a closed position; asecond movable contact for contacting said first movable contact whensaid first movable contact is in said closed position, said secondmovable contact being adapted to receive an electromagnetic repulsionforce from said first movable contact; and a force application memberfor applying a contact force to urge said second movable contact intocontact with said first movable contact, the electromagnetic repulsionforce moving said second movable contact apart from said first movablecontact in opposition to the contact force upon flow of a predeterminedamount of electric current through at least one of said first and secondmovable contacts, and said force application member applying the contactforce to said second movable contact, within a time period after initialseparation of said first and second movable contacts in response to therepulsion force, such that the contact force decreases as the distancebetween said first movable contact and said second movable contactincreases. .Iaddend..Iadd.25. A repulsion type circuit breaker movablecontact device as in claim 24, wherein the rotation moment due to thecontact force applied to said second movable contact by said forceapplication member gradually decreases in correspondence with a degreeof disconnecting said second movable contact from said first movablecontact. .Iaddend..Iadd.26. A repulsion type circuit breaker movablecontact device as in claim 24, wherein the force application membercomprises a contact spring. .Iaddend..Iadd.27. A repulsion type circuitbreaker movable contact device as in claim 26, wherein said secondmovable contact has a rotational pivot, and said contact spring has apoint of application for twisting displaced from the rotational pivot ofsaid second movable contact. .Iaddend..Iadd.28. A repulsion type circuitbreaker movable contact device as in claim 27, wherein said contactspring includes an arm and a coil contact spring, and said secondmovable contact includes a pin, said arm of said contact spring beingengaged with said pin, and upon the moving apart of said first andsecond contacts, said pin slides along said arm towards said contactspring coil. .Iaddend..Iadd.29. A repulsion type circuit breaker movablecontact device as in claim 26, wherein said contact spring exerts aforce and an annular moment on said second movable contact, the annularmoment decreasing upon movement of said second movable contact by theelectromagnetic repulsion force. .Iaddend..Iadd.30. A repulsion typecircuit breaker movable contact device as in claim 24, wherein saidforce application member comprises a twisted torsional coil contactspring.